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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

96

SODIUM CARBONATE

10.  Ammonia.—See Caustic Potash.

11.  Sodium Hydroxide.—3 grams, dissolved in 50 c.c. of water, are
treated with 6 grams of crystallised barium chloride, dissolved in 50 c.c.
of water and the solution shaken and filtered.    The filtrate gives a red
coloration with phenolphthalein if sodium hydroxide is present.    For the
quantitative determination, sec 17 (below).

Traces of caustic alkali are readily detected also by moistening the sample
with a few drops of Dobbin's reagent (yellow coloration). This reagent is
prepared by adding to an aqueous solution of 5 grains of potassium iodide
a solution of mercuric chloride until a. permanent precipitate1: just appears;
after filtration, i gram of ammonium chloride is added and then dilute
sodium hydroxide solution until a precipitate, is formed; after filtering
again, the volume is made up to I litre.

12.  Sodium Bicarbonate.   -A few grains are healed ut about 250°
in a test-tube with a. delivery-tube1 dipping into lime water :   the latter
becomes turbid if bicarbonate' is present.    Quantitative1 determination is
made as with Sodium bicarbonate (3).

13.  Sodium  Sulphide........-The   r : 10 solution  is either treated with

sodium nitropriissiele solution  (violet, coloration) or acitlinVd with elilute
hydrochloric acid and tested with, lead acetate paper (brown coloration).
For quantitative determination, «w 17 (below).

14.  Sodium Sulphite........The i: : 10 solution, containing a little starch

paste, is acielifled with acetic acid and tested with dilute iodine solution
(deceleration).    For quantitative determination, .sw 1:7 (below).

15.  Determination of the Moisture (in calcined or Solvay soda).—
5 grams are heated for 30 minutes at 300" in a platinum crucible innnerseel
in a sand-bath, cooled in a, desiccator and weighed.

16.  Determination of the Strength.

(«) CRYSTALLISED SODA. 5 grams aro dissolved in watesr to i litres,
50 c.c. of this solution (••••• 2-5 grams of substance) being titrated in the
cold with N--hydrochloric acid (methyl orange), i c.c, M-IK/l - • 0-053
gram Na./'(..)., ~ 0-143 gram Naa('().,-|» ioll,,O.

(b) CALCINED SODA.   Kithar of two methods may be used.

1.  English Mdlwtt.    26-5 grams of substance are dissolved in hot water,
the liquid being made up when cold to 500 c.c. and, if 'necessary, filtered ;
50 c.c. of the-  filtrate (: ; 2-65 grams of substance)  are titrated  in the
cold with N-HC1 in presence of methyl orange ;   i c.c. N-acid ™ 2% of
Na8C03.

2.  German Method (Lunge's conditions, adopted by the German soela
manufacturers).    2-65   grams  of  substance,   previously   dehydrated,   are
dissolved in water and the unliltel-ed solution titrated with N 4K"l in presences
of methyl orange:   ,r c.e. N-acid    -2% of Nauroa,

The! value of the soda is expressed in dt'tfm's, expressing the etui lout in sodium
carbonate; en* in sodium oxide*. I'Yeneli or (lay-Lussat: degrees, a,nd also English
degrees, give the percentage of Na^O in the commercial soda,; English degrees
arc, however, slightly greater than the French, tin1 e«inivaleul of .sodium oxide
being taken as 32 instead of 31. German degrees give the content of NaaC'()3.
Lastly, French 1 )escroixilles degrees indicate* the grams of inonohyelrate sul-
phuric acid (!Tj,S04) necessary to neniiraliKe 100 grams of the sotla, Thus, ixceed 2%, otherwise the price is subject